A brushless power generator disclosed in the following Patent Document 1 includes a main power generation winding and an exciting winding that are wound around a stator, a field winding and an auxiliary field winding that are wound around a rotor, a diode that short-circuits the exciting winding of the stator, and a rectifier that rectifies a current flowing from the auxiliary field winding to the field winding of the rotor. According to Patent Document 1, when the rotor starts rotating, an induced voltage is generated on the exciting winding of the stator due to a residual magnetism of a field core of the rotor. Exciting current flows in one direction via the diode and a static magnetic field is generated on the stator. As the rotor rotates in the static magnetic field, an induced voltage is generated on the auxiliary field winding wound around the field core of the rotor. Field current rectified by the rectifier flows through the field winding. Therefore, magnetic poles of N-poles and S-poles are generated on the rotor.
The following Patent Document 2 discloses a reactor connected to a main power generation winding of a stator, which is arranged as a concentrated full-pitch winding, instead of providing the above-described exciting winding on the stator. According to Patent Document 2, when the rotor starts rotating, a residual field of a rotor core induces an electromotive force on the main power generation winding of the stator. The induced electromotive force causes a reactor exciting current that flows, as armature current, in a closed circuit including the main power generation winding and the reactor. As a result, an armature reaction magnetic field is generated. In this case, because the main power generation winding of the stator is the concentrated full-pitch winding, the generated armature reaction magnetic field includes harmonics components (a fifth space harmonics magnetic field). The armature reaction magnetic field including the fifth space harmonics magnetic field interlinks with the auxiliary field winding of the rotor. Accordingly, an electromotive force is generated on the auxiliary field winding. A diode bridge circuit converts the generated electromotive force into a direct current that can be supplied as field current to a field winding of the rotor. Therefore, magnetic poles of N-poles and S-poles are generated on the rotor.
The following Patent Document 3 discloses an arrangement that does not include the above-described auxiliary field winding of the rotor and, instead, uses a diode that short-circuits a full-pitch field winding of the rotor. According to Patent Document 3, when the rotor starts rotating, a residual field of a rotor core induces an electromotive force on the main power generation winding of the stator. The induced electromotive force causes a reactor exciting current that flows, as armature current, in a closed circuit including the main power generation winding and the reactor. As a result, an armature reaction magnetic field is generated. Further, an electromotive force is induced on the field winding of the rotor that is magnetically connected to odd-order space harmonics components of the armature reaction magnetic field. Field current rectified by the diode flows through the field winding. As a result, magnetic poles of N-poles and S-poles are generated on the rotor. Further, the following Patent Document 4 discloses a parallel connection of the above-described full-pitch field windings of the rotor for the purpose of increasing the field current that flows through the field winding.
According to Patent Documents 1 and 2, the exciting winding or the reactor is provided on the stator in addition to the main power generation winding. Further, the auxiliary field winding is provided on the rotor in addition to the field winding. Therefore, the winding structure tends to be complicated, and downsizing the entire winding structure becomes difficult. According to Patent Documents 3 and 4, the auxiliary field winding of the rotor is omitted because the field winding of the rotor is short-circuited via the diode. However, the exciting winding or the reactor is provided on the stator in addition to the main power generation winding. Therefore, the winding structure tends to be complicated. Further, according to Patent Documents 3 and 4, it is difficult to efficiently generate the electromotive force, which is induced by the space harmonics components, on the field winding of the rotor, because the field winding of the rotor is a full-pitch winding. It is therefore necessary to use the exciting winding or the reactor of the stator, other than the main power generation winding, to generate the electromotive force to be induced by the space harmonics components on the field winding of the rotor.
Patent Document 1: JP 62-23348 A
Patent Document 2: JP 4-285454 A
Patent Document 3: JP 8-65976 A
Patent Document 4: JP 11-220857 A